<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>let 命令</title>
 <script>
for (let index of ['张三', '李四'].keys()) {
console.log("index ---> ", index); // 输出下标
}
for (let item of ['张三', '李四'].values()) {
console.log("item ---> ", item); // 输出元素
}
for (let entry of ['张三', '李四'].entries()) {
console.log("entry ---> ", entry); //数组，第一个元素是下标，第二个元素是元素值
 }
 // 我们可以用解构直接获取下标和元素值，推荐用法
 for (let [index, elem] of ['张三', '李四'].entries()) {
 console.log(index, elem); // 输出下标和元素
 }
 </script>
 </head>
 <body></body>
 </html>